Closure device



L. G. BONNER CLOSURE DEVICE Jan. 8, 1957 2 Sheets-Sheet 1 Filed Aug. 6, 1949 l m Q FIC 5.6

LY MAN G- BONNER.

TOR

INYEN AGENT.

Jan. 8, 1957 G. BONNER 2,776,623

CLOSURE DEVICE Filed Aug. 6, 1949 2 Sheets-Sheet 2 9 J LYMAN G.BONNER. INVENTOR.

BY PM AGENT;

United StatesPatent I CLOSURE DEVICE Lyman G. Bonner, Cumberland, Md, assignor to Hercules Powder Company, Wilmington, DeL, a corporationof Delaware Application August 6, 1949, Serial No. 108,984

2 Claims. (Cl. 10249) This invention relates to a frangible, plastic, closure device for a gas-discharging orifice and more particularly to a frangible plastic closure for the discharge nozzles of jet-actuated devices.

With the development of a multi-nozzle, optional thrust unit, it has become necessary to employ some type of nozzle closure which cannot only be removed by remote control, but which can also withstand normal operating pressures without rupturing. With such a closure positioned in each nozzle of an optional thrust unit, it is possible to obtain thrust through the desired discharge nozzle and maintain a seal in the remaining nozzle or nozzles.

Several such closure devices have been suggested but the most effective devices now known comprise a metallic disk or cup positioned in or near the nozzle throat. The disk or cup is usually brazed or welded in place. Immediately prior to employing the thrust unit, a standard blasting cap is positioned against the disk or cup. Then, when thrust is needed, the blasting cap is shot to puncture the disk or cup.

This metallic-type closure has several disadvantages which make it unsatisfactory. Most important, the blasting cap does not always completely separate the metal closure from the nozzle wall. Consequently, the residual metal causes jet disturbances which aifect the efficiency of the gaseous discharge. Furthermore, the flying pieces of the ruptured metal strike the powder charge and sometimes cause fracture of the grain with a resultant breakup during combustion of the charge. The flying particles also constitute a hazard to both material and personnel, whether used in jet-assisted take-off units or when used at any time on the lightly constructed gliders for which optional thrust units are primarily intended. In addition, it is difiicult to effect a moisture-proof seal with a metallic closure and at the same time have a closure which can be readily and completely removed by the force of a blasting cap.

Now in accordance with the present invention, a nozzle closure device may be made which is readily and completely pulverized, and which will operate simultaneously as a pressure seal and moisture seal, and as a pressure releasein the event of generation of excessive pressure within the gas-producing unit. The device of the present invention may also be adapted to house ignition materials for the ignition of the gas-producing charge.

Generally described the present invention is a frangible, plastic, closure device for a gas-discharging orifice which comprises a diametrically converging body member and a well adapted to receive an electric initiator extending longitudinally from the convergent end to a point short of the divergent end thereof. This frangible, plastic, closure device is positioned within the discharge nozzle of the jet-actuated device so that the converging surface of the body member registers with the converging interior surface of the discharge nozzle. The device is maintained in position and a gas pressure seal effected by any suitable means, such as those hereinafter disclosed. The closure Patented Jan. 8, 1957 ice device, according to this invention, may have a concavity disposed in the divergent end adapted to house the ignition charge for igniting the gas-producing charge. The concavity may have an integral housing extending from its inner surface to hold the ignition composition or a separate container for the ignition composition may be ccmented or otherwise secured within the concavity. The body member may be made to curve slightly inward toward its longitudinal axis at the divergent end in order that a sealing or calking compound maybe packed be tween the body member and the discharge nozzle wall to enhance the pressure and moisture seal. The body member may be in the form of a cone designed to fit the converging interior surface of the discharge nozzle, or may comprise a partial conical section having a projection extending longitudinally from the converging end. This projection may be cylindrical or may have any other desired configuration.

The body member may be provided with a region or regions of relative weakness by means of grooves which extend into the body member in the direction of its divergence and which terminate short of the surface of the divergent end or the inner surface of the concavity disposed in the divergent end. Such regions of Weakness may also be formed by means of grooves which extend from the surface of the divergent end of the body member or the surface of the concavity therein disposed and terminate short of the convergent surface. By varying the thickness of the body member between the base of the grooves and the surface of the divergent end or converging surface, as the case may be, the region or regions of relative weakness defined by the grooves may be ruptured and expelled at predetermined internal pressures. In this manner, a safety release may be integrally fabricated in the closure device which will function in the event of a pressure generation in excess of that for which the gas-producing unit was designed.

Despite the specific design of the body member closure device, a well adapted to retain an electric initiator extend longitudinally from the convergent end of the body member to a point short of the surface of the divergent end or the inner surface of the concavity disposed in the divergent end. The thickness of the section of the body member between the base of the well and the surface of the divergent end or the inner surface of the concavity depends on the particular application and the strength of the initiator employed.

The preferred electric initiator employed to pulverize the frangible, plastic, closure devices is also part of the present invention. Generally described this initiator comprises in combination a base charge of black powder and a superimposed charge of crystalline, detonative explosive. The preferred embodiment of the initiator comprises a shell, a base charge of black powder, a charge of crystalline, high explosive superimposed upon the black powder, a priming charge superimposed upon the crystalline explosive, an ignition charge superimposed upon the priming charge and a hard, dielectric ignition plug. In the preferred embodiment the shell is crimped over the top of the ignition plug. When the initiator is fired, the closure device is pulverized by the detonation of the crystalline, high explosive, the ignition compound in the concavity is ignited by the flash-through of the black powder, and the gas-producing charge is thereby ignited. The nozzle throat is completely cleared by the detonation of the initiator and the initial flow of combustion gases from the ignited gas-producing charge. The closure devices in the remaining nozzle or nozzles of the jet-actuated device withstand any normal pressure generated during combustion of the charge and act as pressure and moisture seals.

In the accompanying drawings, Fig. 1 represents a sectional view of the preferred embodiment of the frangible, plastic, closure device of the invention. Figs. 2 and 3 respectively represent plan views of the convergent and divergent ends of the device shown in Fig. 1. Figs. 4, 5 and 6 represent sectional views of other embodiments of the closure of the invention. Figs. 7 and 8 represent part sectional, part elevational views of further embodiments of the invention. Fig. 9 represents a sectional View of an embodiment of the electric initiator which is also part of the invention. Fig. 10 represents a part elevational, part sectional view of the device of Fig. 1 in its operative position.

In Figs. 1, 2 and 3 a frangible, plastic, closure device is shown which has a body member 10 comprising a concavity 11 at one end thereof, and which diametrically converges toward the opposite end. An annular housing 12 extends longitudinally from the inner surface 13 of the concavity 11. A cylindrical projection 14 extends longitudinally from the convergent end of the body member 10, the terminal end of which is provided with threads 15 to engage the positioning means or to accommodate an internally threaded cover, not shown. A region of relative weakness in the central portion of the body member 10 is provided by the annular groove 16 extending longitudinally into the body member from the convergent end, the inner wall of which is defined by the outer surface of the projection 14. A well 17 extends longitudinally into the projection 14 to a point short of the inner surface 13 of the concavity 11.

In Fig. 4 a frangible, plastic closure is shown which has a body member 40 containing a concavity 41 at one end thereof, and which diametrically converges toward the opposite end. A cylindrical projection 42 extends longitudinally from the end of the body member 40 opposite the concavity 41, the terminal end of which is provided with threads 43 to engage the positioning means or to accommodate an internally threaded cap, not shown. A region of relative weakness in the central portion of the inner cavity wall is provided by an annular groove 45 extending longitudinally into the body member, the inner wall of which is defined by the outer surface of the projection 42. A well 46 extends longitudinally into the projection 42 to a point short of the inner surface 44 of the concavity 41.

In Fig. 5 a frangible, plastic closure is shown which has a body member 50 containing a concavity 51 at one end thereof, and which diametrically converges toward the opposite end. An annular housing 52 extends longitudinally from the inner surface 53 of the concavity 51. The convergent end of the body member is externally threaded to accommodate the internally threaded positioning member 54. The divergent surface 55 of the positioning member is designed to register with the surface of the discharge nozzle (not shown) which diverges from the nozzle throat to the egress orifice. A well 56 extends longitudinally into the convergent end of the body member to a point short of the inner surface 53 of the concavity 51. An electric initiator 57 is disposed in well 56 and the lead wires 58 pass through the aperture 59 of the positioning member 54.

In Fig. 6 a frangible, plastic closure is shown which has a body member 60 containing a concavity 61 at one end thereof, and which diametrically converges toward the opposite end. A cylindrical projection 62 extends longitudinally from the end of the body member 60 opposite the concavity 61. A well 63 extends longitudinally into the projection 62 to a point short of the inner wall 64 of the concavity 61.

In Fig. 7 a frangible, plastic closure is shown which has a body member 70 containing a concavity 71 at the end thereof, and which converges diametrically toward the opposite end. The convergent end is equipped with threads 72 to engage a positioning means or to receive an internally threaded cap, not shown. A well 73 extends longitudinally into the convergent end to a point short of the inner wall 74 of the cavity 71. An electric initiator 75 is disposed in the well 73. A cellulose acetate housing 76 is secured to the inner wall 74 of the concavity 71 by a layer of sealing compound 77. The housing 76 contains an ignition composition 78 for the gasproducing charge, not shown, and is sealed by a cellulose acetate tape 79.

In Fig. 8 a frangible, plastic, closure device is shown which has a body member 80 which converges diametrically toward one end. A cylindrical projection 81 extends longitudinally from the body member 80 to form the convergent end. A well 82 extends longitudinally into the projection to a point short of the surface 83 of the divergent end of the body member 80. An electric initiator 84 is disposed in the well 82. An annular groove 85 extends longitudinally into the body member 80 around the base of the projection 81 to a point short of the surface 83 of the body member to provide a region of relative weakness.

In Fig. 9 is shown an electric initiator for use with the frangible, plastic closures of this invention. In the bottom of the bronze shell is disposed a charge of black powder 91. Superimposed thereupon is a charge 92 of pentaerythritol tetranitrate. Upon the charge of pentaerythritol tetranitrate is disposed a priming charge 93 of diazodinitrophenol and potassium chlorate, and disposed upon the priming charge is a loose ignition mixture 94 of lead and selenium in stoichiometric proportions. An ignition plug assembly comprising a hard, resinous, dielectric plug 95, lead wires 96, and bridge wire 97 completes the initiator. The shell 90 is crimped over the plug 95. The lead wires 96 and bridge wire 97 extend from the plug and into the ignition mixture 94.

Fig. 10 shows the closure device of Fig. 1 in operative position. An electric initiator 100 is disposed in the well 17 and the housing 12 is filled with an ignition composition 101 consisting of powdered potassium chlorate. The housing 12 is sealed with a cellulose acetate tape 102. The device is positioned in the discharge nozzle 103 by a body of cast, polyester resin 104. A gas pressure seal is effected by a zinc chromate base calking compound 105.

Having specifically illustrated several embodiments of the invention, the following examples are given for the purpose of further illustration.

Example 1 Frangible, plastic, closure devices were prepared similar to that illustrated in Fig. 8 by standard molding procedures using a phenol-formaldehyde molding powder (Bakelite molding powder No. BM Rounds of double-base smokeless powder which consisted of a cylindrical, singly-perforated grain 23% inches in length and having an outer diameter of 5.27 inches and an inner diameter of 2.87 inches, and concentrically disposed within the perforation thereof, a solid cylindrical grain 23 /2 inches in length and 2.4 inches in diameter, were fired in a suitable chamber with a closure device in each of two nozzles located at opposite ends of the chamber. A thin cellulose acetate cylinder containing 9 grams of a 60/40 magnesium perchlorate/potassium perchlorate mixture was cemented to the surface of the divergent end of each of the closure devices. The closure devices were placed in the discharge nozzles with their convergent surfaces registering with the convergent surfaces of the nozzles and were positioned in the nozzles with a body of cast resin such as that shown in Fig. 10. An electric initiator similar to that shown in Fig. 9 and having a base charge of 0.6 gram of black powder was placed in the well of each closure device. The initiator at one end was fired. The resulting shock and flash pulverized the plastic closure and at the same time ignited the metal oxidant igniter material encased in the cellulose acetate cylinder cemented to the surface of the divergent end of the closure device. This served to ignite the main propelaft'r'aeaa lent charge with no significant ignition delay. The igniter material in the cellulose acetate cylinder cemented to the other closure device was also ignited but had no deleterious effect on the closure device or its sealing relationship with the discharge nozzle. The remaining plastic closure device completely sealed the alternate discharge nozzle throughout combustion. The chamber pressure was 1100 p. s. i. and the burning time was approximately 3 seconds.

Example 2 Plastic closure were prepared similar to that illustrated in Fig. 5 by standard molding procedures using the molding powder of Example 1. These closure devices were tested with the same gas-producing charge as in Example 1 and in a similar chamber equipped with a discharge nozzle at each end. Nine grams of the ignition mixture employed in Example 1 was placed in the housings at the divergent end of each of two of the devices and sealed therein with a strip of cellulose acetate tape. One of these devices was positioned in each discharge nozzle with the convergent surface of the body member registering with the nozzles inner convergent surface and with the divergent surface of the positioning member registering with the divergent surface of the nozzle exteriorly of the nozzle throat. The pressure seal was enhanced by a zinc chromate calking compound applied as shown by numeral 105 of Fig. 10. As in Example 1, the closure device at one end was broken by the initiator shown in Fig. 9 containing 0.6 gram of black powder as a base charge. The flash-through of the black powder ignited the metal oxidant igniter mixture at the divergent end of the plastic closure which in turn ignited the powder charge without significant ignition delay. The plastic closure positioned within the alternate nozzle again acted as an efficient pressure seal for the duration of burning. The igniter composition contained within the housing of this closure device was ignited during combustion but had no deleterious effect of the device or the seal effected thereby. As in Example 1 the chamber pressure was 1100 p. s. i. and the burning time about 3 seconds.

Example 3 Plastic closures similar to those illustrated in Fig. 4 wereprepared by standard molding procedures using the molding powder employed in Example 1. These closure devices were tested under conditions similar to those in Example 1. The igniter composition was placed in the concavity at the divergent ends of the closure devices and sealed therein by cellulose acetate tape as in Example 2. One of these units was positioned in each of the discharge nozzles by means of a body of cast resin as in Example 1 and as illustrated in Fig. 10. The special electric initiator pulverized the closure device at the desired end and ignited the ignition composition contained in the concavity of its body member, which in turn ignited the powder charge. The unruptured device in the alternate nozzle effected an efficient pressure seal throughout the combustion of the gas-producing charge. The ignition of the igniter material in the unruptured device exhibited no effect on the device itself or the pressure seal effected thereby.

Example 4 In order to determine the fragment size of the various plastic closures which may be fabricated in accordance with the invention, several of the different types of closure devices Were placed individually in a suitable container and ruptured with the special initiator shown in Fig. 9. In all of these tests the closure devices were reduced to fragments, none of which could possibly obstruct a discharge nozzle throat and thus prevent passage of the combustion gases or otherwise effect a diminution in the efiiciency of the jet.

Example 5' Bursting Pressure (,p. s. 1.)

Thickness of the Portion of Relative Weakness The design of the frangible, plastic, closure device of this invention is not limited to those illustrated, since it is obvious that any number of suitable shapes may be designed depending upon the particular application. The critical elements of design, however, exist in the necessity for all of the closure devices to diametrically converge toward one end to present a surface which will register with the internal surface of the particular discharge nozzle employed to form a tight fit in or interiorly of the discharge nozzle throat. It is also necessary to the invention that the device contain an initiator well extending longitudinally from the convergent end toward the divergent end of the closure device to a point short of the surface of the divergent end which faces into the interior of the gas-generating device. Unless the well does extend into the closure device substantially parallel to its longitudinal axis, uniformly complete breakage is not obtained. When the special initiator of the invention is employed, the longitudinally extending well is further necessary to insure positive ignition of the igniter composition by the black powder charge and a substantially instantaneous ignition of the gas-producing charge within the combustion chamber. The thickness of the section of the body member of the closure device between the base of the grooves employed to provide a section of relative weakness and the surface of the divergent end or the inner surface of a concavity therein will depend, as fully illustrated in Example 5, upon the pressures at which the gas-generating device is designed to operate.

It is, of course, obviously essential to the invention that the plastic material from which the device is fabricated be completely frangible under the shock of the exploding initiator. In this regard the material of construction is not limited to phenol-formaldehyde resinous material or the particular materials employed in the examples, but may be of any frangible material, the physical properties of which are not subject to variation at the temperatures encountered. Nonlinear polymeric materials such as the melamine-, urea or polyester-type resins are generally operable. Most linear polymers are not satisfactory where the closure devices are to be used for gas pressure seals and safety devices as well as for moisture seals and ignition agents. Consequently, linear polymers such as methyl methacrylate and polystyrene are operable as long as they are not subjected to temperatures high enough to effect a change in their physical properties. It is obvious that slight modifications in dimensions would be necessary with the different ma- 7 terials to give a performance identical to that of the closure devices illustrated in Example 5, particularly in the thickness of the body member at the point of relative weakness. However, such modifications are within the skill of the art.

The material employed to position the frangible, plastic closure in the discharge nozzle may be any substance which is itself frangible or may be readily dislodged from the nozzle throat by the combined action of the electric initiator and the initial flow of combustion gases. A cast, polyester positioning body, such as that illustrated in Fig. 10, is preferred. If a calking compound is employed to enhance the pressure and moisture seal, that compound should be sufficiently heat-resistant to withstand the temperatures of the combustion gases within the gas-producing device. Zinc chromate base compounds are very satisfactory and are preferred.

With the exception of the black powder base charge the other parts of the special electric initiator, which constitutes a part of the present invention, may be constructed from materials which are equivalent to those disclosed. For example, the shell may be made from brass or aluminum instead of bronze, the explosive may be cyclonite or tetryl instead of pentaerythritol tetranitrate, the priming charge may consist of any of the well known materials which are detonatable by heat, and the ignition composition may be any operable ignition mixture instead of lead-selenium. While it is possible to also substitute a different type of ignition plug for that disclosed in Fig. 9 and while it is also possible to employ the various sealing means known to the art such as layers of asphalt and sulfur, it is preferred to employ a hard, resinous plug, as shown in Fig. 9, held in place by the crimped shell. The use of such an ignition plug allows a much shorter initiator which is preferred for obvious reasons. In general, however, an initiator comprising a bronze shell, a black powder base charge, a pentaerythritol tetranitrate explosive charge, a diazodinitrophenolpotassium chlorate priming charge, a lead-selenium ignition composition, and the hard, resinous, dielectric ignition plug held in place by the crimped shell has been found to be completely satisfactory in all respects and is preferred.

The advantages of the frangible, plastic closures of this invention for optional direction thrust units and various other rocket applications are many. Among the primary advantages is the absence of missile hazards since the frangible, plastic closures disintegrate completely under the shock of the electric initiator. In this regard there is absolutely no danger of metallic fragments causing fractures in the powder charge. A second important advantage is that it is impossible for fragments to remain in the nozzle throat and create jet disturbances. A more uniform bursting pressure is obtained with this type of closure than with the metal disk of the prior art. In addition, the use of the special blasting cap of the invention permits a simple ignition circuit with no leads extending through the firing chamber or the closure. The result is a greatly enhanced moisture and pressure seal.

While the invention has been particularly described and illustrated with reference to the optional direction thrust unit, the application for which it has greatest utility, it is to be understood that the closure devices disclosed and claimed have utility in a wide variety of gas-producing and jet-actuated devices.

Since many modifications can obviously be made in the frangible, plastic, closure device disclosed without departure from the scope of this invention, the invention is to be limited only by the scope of the invented claims.

What I claim and desire to protect by Letters Patent is:

1. A frangible plastic closure device fora gas-discharging orifice which in combination comprises a diametrically converging body member, an initiator well extending longitudinally from the convergent end to a point short of the divergent end of the body member, an annular groove disposed around the well and extending longitudinally into the body member to a point short of the divergent end of the body member to provide a central region of relative weakness, and container means associated with the divergent end of the body member to accommodate ignition composition for a smokeless powder charge.

2. A device in accordance with claim 1 in which the said means consists of a hollow concavity in the divergent end of the body member and an annular housing for ignition composition extending from the surface of the concavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,317,610 Barlow Sept. 30, 1919 1,559,822 Wiley Nov. 3, 1925 2,086,548 Handforth July 13, 1937 2,123,691 Burrows July 12, 1938 2,422,090 Fuess June 10, 1947 2,452,892 Appleton Nov. 2, 1948 2,457,839 Skinner Jan. 4, 1949 2,462,135 Skinner Feb. 22, 1949 

